"They would want routine measurements of the air quality in the classroom -- in their son or daughter's classroom - in the gymnasium," says Gerrick Monroe, the school's chief operating officer. "Some have even asked for bus readings."

Monroe showed us a $5 million dome built to enclose a playground and filter the air.

Kids play in the dome built by the International School of Beijing.
CBS News

"Our parents were concerned, given the, at times, 10 to 15 days in a row that our kids would be inside and not released for recess," Monroe says. "We needed to have another option."

Watch: China pollution pushing some foreigners out, below.

China pollution pushing some foreigners out

The school spends roughly $150,000 a year on air filter systems. But the average Beijinger cannot afford that. Mindy Wu has a single, $120 air filter in her bedroom.

"I'm worried, I have to say," she says.

Asked if she has considered moving to a less-polluted place, she replies, "Honestly, yes. But it's not a kind of easy decision to make, because moving your home is like moving your whole life to a different place."

The Chinese government set targets for heavily polluting industries to reduce emissions by 30 percent in five years. It's an effort to prevent Beijing from becoming a modern-day forbidden city that no one dares to enter.